A world within the Metaverse created by Masayoshi Shido. The Phantom Thieves of Hearts plan a heist to steal Masayoshi's heart in order to reform him before he can be elected as Japan's next Prime Minister and instill his radical policies. The dungeon takes the form of a luxury cruise ship with the National Diet Building sitting atop it. The boat floats in a massive sea that engulfs all of Japan. The skyscrapers in the immediate vicinity of the building float half submerged in the water, occasionally being crushed by the oncoming vessel. The Thieves comment that Shido does not really care about the future of the country as he claims in reality but only wants to save himself and his wealthy patrons on an ark.

The team finds that they require five letters of introduction to access the Representative Chamber where Shido's Treasure lies within. These letters are held by Shido's most trusted allies within the Conspiracy who appeared in the hotel where the protagonist, Morgana, Ryuji and Ann celebrated their first victory as Phantom Thieves. After the defeat of the first of them, it becomes apparent that the VIPs aboard the ship are not those of Cognitive existences, but rather direct manifestations of the person's Shadow Self, able to appear due to their powerful bond with Shido.

Each of the VIPs also reveals their part of their scheme within the Conspiracy. Politician Ooe explains the subway train pilot rampages are attempts to remove the previous Minister of Transport from office while Shido criticizing his mismanagement. TV Station President reveals that Junya Kaneshiro had donated a large sum of money to Shido which explains Kaneshiro's impunity before his reformation and that Shido profited greatly from the artwork of Ichiryusai Madarame. IT Company President played Medjed because they already know the Phantom Thieves cannot target anonym and their original plan is to admit defeat on the day of Cleanse to boost the popularity of the thieves to a new height. Futaba Sakura's hacking into the imposter's Medjed website is a miscalculation which they did not care much. He is also responsible for encrypting Wakaba Isshiki's research on the world of cognition and uploading it to a secret domain before it was destroyed. Like Kunikazu Okumura, all of these connections had donated money to or cooperated with Shido in assassinations by mental shutdown of their competitors.

Shido's Treasure is his legislator's pin which takes the shape of a golden helm's wheel floating above the ship. This is reflective of his warped view that he is the only person who can "steer Japan" in the right direction. After the defeat of his Shadow Self, the real Shido takes a medicine to enter suspended animation in order to kill the Phantom Thieves and prevent the Treasure from being stolen, but the Thieves escape in time and Shido begins to repent his actions. The pin itself, however, has no monetary value, leaving the Thieves unable to sell it.

The top floor where the showdown with Shadow Shido takes place acts as one of the dancing stages of the game, for the song Rivers in the Desert. The engine room where Goro Akechi was fought in acts as one of the DLC stages for him.

The submerged city symbolizes both the progressively rising sea level because of climate change and the economic state of Japan which is still struggling to recover from the burst of asset price bubble in 1992.

It might also symbolize Shido's disregard for the future of Japan, letting the entire nation sink into the sea while only he and his associates survive in his ark.